Communication systems, such as land mobile radio and cellular communications systems, are well known. Such systems typically include a plurality of radio communication units (e.g., vehicle-mounted mobiles or portable radios in a land mobile system and radio/telephones in a cellular system), one or more base stations/repeaters (usually located at a fixed base site) and other equipment used in the processing and monitoring of communications. The base stations are typically connected to other fixed portions of the system (i.e., the infrastructure) via wire connections and communicate with communication units and/or other base stations within the coverage area of their respective sites via wireless link(s).
Generally, the amount of information that may be carried by any communication system is a function of the available bandwidth. In recent years, wireless communication systems having increasingly wide signal bandwidths (called wideband systems) have been developed to transmit increasing amounts of information across wireless link(s). For example, wideband systems have been developed to support communication of streaming voice and video over wireless link(s), enabling communication units to participate in voice calls, video calls, web browsing, video-conferencing and/or internet communications with other communication units or infrastructure devices. Oftentimes, wideband systems use multi-carrier modulation whereby the information is divided into a plurality of sub-channels. Larger bandwidths may be accommodated by increasing the number of sub-channels, to the extent that the bandwidth of the total number of sub-channels does not exceed the available bandwidth.
A problem associated with wireless communication systems, and especially wideband systems, is that the power required for communication units to receive and process a signal is roughly proportional to the bandwidth of that signal. This is a concern because communication units are usually powered by limited power supplies (e.g., batteries) that are challenged, even in narrowband systems, to provide power for an eight-hour work day. As an illustration, in a wideband system using multi-carrier modulation with 24 sub-carriers, a communication unit desiring to process the signal will require approximately 24 times greater processing power than would be required in a narrowband private radio system, such as an APCO 25 trunking system. Hence, battery life will be expended roughly 24 times faster in the wideband system than in the narrowband system.
Thus, there is a need for a system and method for communicating messages in wireless multi-carrier communication systems in a manner that enables reduced power consumption of receiving devices (e.g., wireless communication units). Advantageously, the system and method will not introduce significant delays that would counteract the ability of the communication unit to support voice calls, video calls, web browsing, video-conferencing and/or internet communications. The present invention is directed to addressing these needs.